I don't know the size, but I know how to find out
Take the old packing out. You will need some tool with a hook on the end to fish the stuff out. That's the hard part. I like the pullers whose shaft is a tightly wound spring. Most of the old packing will be intact. Measure it with a ruler, and take it down to the chandlery, so that you get new packing the same size. This assumes the previous packing was correctly sized, which is almost certain was if one loop fit tightly in the space between the gland and shaft. (You'll see when you pull it out.) When you put the new packing in, make sure each ring is pushed all the way back before inserting the next ring. Stagger the ring ends around the shaft at 0*, 120*, and 240*. You won't do this perfectly, and the butts won't be as neat as you think, and don't worry about it. This ain't brain surgery.
